Fender material

Abstract

To provide a fender which is a bow fender equipped in a worker transport ship used for management and maintenance of an offshore wind power generation facility, and has predetermined aboardage performance.SOLUTION: The present fender is a fender for a worker transport ship operated alongside a facility provided in a water area, wherein a rubber composition forming a surface layer part of the fender contains hollow ceramic balloons, and the ceramic balloons broken by polishing are scattered on a surface of the rubber composition. The polished surface of the rubber composition preferably has an Ra of 2 to 7 μm and an Rt of 20 to 100 μm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fender, and more particularly to a bow fender for a crew transport ship that is operated alongside a facility located in a water area. [Background technology]

[0002] Generally, a ship's side is defined as the side of a ship (Kojien dictionary). Fenders are installed to prevent damage to both ships and mooring facilities when ships approach or are moored at mooring facilities, and rubber fenders are commonly used in Japan (Non-Patent Document 1). Patent Document 1 proposes a fender comprising a rubber fender body and a surface layer disposed on at least the impact-receiving surface of the rubber fender body, the surface layer being a layer of 2 mm or more in thickness made of a first synthetic resin with a lower coefficient of friction than the rubber constituting the rubber fender body. It also describes that the coefficient of friction of the surface layer, measured in accordance with ASTM D1894, is 0.3 or less, preferably 0.2 or less.

[0003] Patent Document 2 proposes a rubber fender characterized by an ultra-high molecular weight polyethylene plate being integrated by vulcanization bonding at the part that receives impact with a ship, with multiple grooves formed on the surface of the ultra-high molecular weight polyethylene plate. It also describes that ultra-high molecular weight polyethylene has a friction coefficient μ (JIS K7125) of 0.2 and is highly resistant to abrasion, impact, and weather, making it a resin material suitable for absorbing impact at the part that receives impact.

[0004] Such fenders are installed to protect ships and mooring facilities by absorbing and mitigating the impact forces generated when ships dock or moor, and the coefficient of friction itself is generally not an issue. However, as shown in Patent Documents 1 and 2, rubber fenders may be equipped with a low-friction coefficient material on the rubber surface to prevent wear on the rubber portion and to disperse and reduce impact forces. In such cases, the friction coefficient to be selected becomes an issue. In contrast, the coefficient of friction is particularly important for automobile tires and brake pads. For example, the coefficient of friction μ acting on the contact surface between a tire and road surface is generally considered to be around μ = 0.8 on dry paved roads, 0.6 to 0.4 on wet paved roads, 0.5 to 0.2 on snow-covered roads, and 0.2 to 0.1 on icy roads (DUNLOP Tire-Related Knowledge, Tire-Related Glossary, Friction Coefficient).

[0005] Incidentally, as part of the recent promotion of green energy, Japan has also been called upon to promote offshore wind power generation, and guidelines such as the CTV Safety Design Guidelines (Non-Patent Document 2) have been published. These guidelines state, "In accordance with Japan's Green Growth Strategy, a target of 30-45 GW of offshore wind power generation has been set by 2040. As the construction and operation of offshore wind power generation plants gains momentum, demand for vessels used in installation and maintenance is expected to expand. ... Various work vessels are used in the construction and maintenance of offshore wind power plants. Among these, crew transfer vessels (CTVs), which are used in many stages of the project, are relatively small vessels and are therefore expected to be built by small and medium-sized shipyards. Meanwhile, because offshore wind power generation was first introduced and expanded in Europe, CTVs built to date have been designed to European standards and equipped with European products. For this reason, in order to establish a domestic supply chain, it is necessary to domestically produce CTVs and their onboard equipment."

[0006] Non-patent document 2 states that the target vessels are "relatively small CTVs with a maximum capacity of approximately 27 people that will sail along the coast of Japan, on the premise that they will comply with the provisions of the IP Code adopted by the IMO and scheduled to come into effect on July 1, 2024 (IMO (International Maritime Organization)). In the section on facilities and equipment, it states that the bow fenders will be installed on OWTs (Offshore Wind Power Generation Facilities)." The document states, "The CTV will be equipped with bow fenders that minimize impact when coming alongside the OWT and maintain appropriate friction while the bow is pressed against the ship. When the fenders are compressed while the OWT is coming alongside (while the bow is pressed against the ship), appropriate clearance and step distance between the ladder and the ship will be ensured. In the performance section, "commencement performance" refers to the ability of the CTV to safely approach and come alongside the OWT while controlling its hull attitude in relation to wind, currents, and waves, and to maintain a stable state of coming alongside even in rough waves in order to safely transfer personnel. The safe docking of the CTV to the OWT and the safe transfer of personnel are particularly important among CTV personnel. It is necessary to evaluate the bow oscillation performance during the transfer and pay attention to minimizing bow oscillation during the transfer to ensure the safety of the personnel." [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-271325 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-156250 [Non-Patent Document 1] National Land and Infrastructure Policy Research Paper No. 1101 March 2020 (YSK-N-424) [Non-patent document 2] CTV Safety Design Guidelines (Maritime Bureau, Ministry of Land, Infrastructure, Transport and Tourism, March 2020) Summary of the Invention [Problem to be solved by the invention]

[0008] Not only is the number of offshore wind power plants expected to increase in the future, but it is also believed that there will be many opportunities for crew transport vessels to be used for management and maintenance at offshore wind power plants. The bow fenders installed on crew transport vessels, as described in Non-Patent Document 2 above, are installed in different locations than the conventional marine fenders described in Patent Documents 1 or 2 or Non-Patent Document 1, and their uses and functions are not necessarily the same. Rather, in order to achieve the required fendering performance, they are thought to have characteristics similar to automobile tires or brakes. The present invention aims to provide a fender for crew transport vessels operated at facilities installed in specific waters, based on Non-Patent Document 2. [Means for solving the problem]

[0009] The fender of the present invention is a fender for a worker transport ship that is operated alongside a facility installed in a water area, and the rubber composition that forms the surface layer of the fender contains hollow ceramic balloons, and the surface of the rubber composition is polished so that broken pieces of the ceramic balloons are scattered throughout.

[0010] In the above invention, the polished surface of the rubber composition preferably has an Ra of 2 to 7 μm and an Rt of 20 to 100 μm.

[0011] The rubber composition preferably contains 1 to 15 mass % of ceramic balloons.

[0012] The ceramic balloons preferably have a particle size distribution of 20 to 300 μm and a breaking stress of 100 to 300 MPa.

[0013] The rubber composition is preferably a rubber containing at least one of chlorosulfonated polyethylene rubber (CSM) and chloroprene rubber (CR), or a rubber obtained by adding carbon black or silica to any of the above rubbers.

[0014] The fender according to the present invention is for a crew transport ship that is operated alongside a facility installed in a water area, and the rubber composition forming the surface layer of the fender contains hollow ceramic balloons, and has a static friction coefficient of 0.4 to 1.2 and a dynamic friction coefficient of 0.3 to 0.7 in a wet state. The friction coefficients were determined using a wet friction tester manufactured in-house.

[0015] The fender according to the present invention is a fender to be installed on a worker transport ship that is operated alongside a facility installed in a water area, and the surface layer of the fender comprises the following ceramic balloon-containing rubber composition. The ceramic balloon-containing rubber composition has a coefficient of friction in a wet state that is 1.2 to 2.4 times higher in static friction and 1.5 to 3 times higher in dynamic friction than the coefficient of friction of the rubber composition itself that does not contain ceramic balloons. The coefficient of friction was determined using a wet friction tester manufactured in-house. [Effects of the Invention]

[0016] The rubber composition of the surface layer of the fender according to the present invention has a high coefficient of friction in a wet state, and therefore the fender according to the present invention can be suitably used as a fender for the crew transport ship described in Non-Patent Document 2, for example, as a bow fender for a crew transport ship operating in waters with a significant wave height of more than 1.5 m. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is an explanatory diagram showing a worker transport ship equipped with a fender according to the present invention coming alongside an offshore wind power generation facility. [Figure 2] FIG. 2(a) is an explanatory diagram showing the configuration of a fender according to the present invention, and FIG. 2(b) is an explanatory diagram showing the surface state of the fender. [Figure 3] 1 is an explanatory diagram showing the characteristics of a ceramic balloon according to the present invention. [Figure 4] FIG. 1 is a schematic diagram of a friction coefficient testing machine. [Figure 5]1 is a graph showing the relationship between the applied load and the wet static friction coefficient for a rubber composition or a rubber composition containing ceramic balloons. [Figure 6] 1 is a graph showing the relationship between the number of rotations of a test roller and the wet dynamic friction coefficient for a rubber composition or a rubber composition containing ceramic balloons. [Figure 7] 1 is a graph showing the results of a surface roughness measurement test of an example of the invention and a comparative example. [Figure 8] 10 is a graph showing the results of a test to confirm the mooring performance of a crew transport ship equipped with fenders. DETAILED DESCRIPTION OF THE INVENTION

[0018] The following describes embodiments of the present invention. Unlike conventional rubber fenders installed to prevent damage to both ships and mooring facilities when ships berth or moor at mooring facilities, the fender of the present invention is used, particularly as a bow fender for crew transport vessels (CTVs) used for maintaining offshore wind farms (OWTs). The surface layer of the fender of the present invention is made of a rubber composition containing ceramic balloons, and the surface of the rubber composition is polished to expose fracture surfaces scattered with the ceramic balloons. This surface layer configuration allows the fender, even in a compressed state, to ensure appropriate clearance and step distance between the OWT ladder and the ship, even in rough waves, enabling the CTV to safely berth and the crew to safely transfer to the OWT, thereby achieving the desired mooring performance. Figure 1 shows a crew transport vessel equipped with the present invention berthing alongside an offshore wind farm. The fender according to the present invention is arranged on the bow of a crew transport vessel (CTV) as shown in Figure 1, and exhibits specified mooring performance when the CTV comes alongside the landing area on the wind turbine side of an offshore wind farm (OWT).

[0019] As shown in FIG. 2(a), the fender 10 according to the present invention has a base portion A and a surface layer portion B. The base portion A constitutes the main body of the fender 10 and supports the surface layer portion B. The base portion A can be made of known materials such as steel plate or synthetic resin. The surface layer portion B contains ceramic balloons 15 in a rubber composition 11. The surface of the surface layer B is polished, and the ceramic balloons 15 contained in the rubber composition 11 are broken, resulting in scattered broken ceramic balloons 151. The rubber composition 11 may also contain additives 17, such as carbon black or silica, which may be scattered on the surface of the surface layer B. FIG. 2(b) shows a micrograph (magnification: ×50.0) of the polished surface of the surface layer B. Scattered ceramic balloons (CB) can be seen in FIG. 2(b). Broken CBs with exposed fracture surfaces and unbroken CBs are also observed. The 120 μm and other values ​​in the figure indicate their sizes.

[0020] It is preferable that the ceramic balloons 15 do not break during kneading with the rubber composition, break appropriately when polished after molding the rubber composition, and have broken ceramic balloons with a predetermined strength and shape scattered on the polished surface. It is also preferable that the ceramic balloons 15 are easily available. For example, commercially available ceramic balloons are disclosed on the Tomoe Engineering Co., Ltd. website (https: / / www.tomo-e.co.jp / upload / cProductsJA / 25QU021-cProductsJA_content-002.pdf), Seishin Corporation website (https: / / www.betterseishin.co.jp / product / chemical / hollow_glass_beads / ), and Taiheiyo Cement Corporation website (https: / / www.taiheiyo-cement.co.jp / service_product / espheres / es_2.html), etc. Additionally, "Preparation and Applications of Ceramic Hollow Particles, Chapter 5: Strength of Ceramic Hollow Particles" (by Takayuki Kato, Nagasaki University Academic Research Repository) provides a detailed explanation of the properties of commercially available ceramic balloons (commercial alumina bubbles, fly ash (TV09), shirasu balloons (Terra Balloon A), and alumina hollow particles (Al2O3-5wt%SiO2) produced by the mechanofusion method). This technical document provides useful information on the properties of ceramic hollow particles (Tables 5-1 and 5-2, Figure 5-3) and the particle strength of ceramic hollow particles (Figure 5-4).

[0021] Preliminary tests were conducted on commercially available ceramic balloons to examine their kneadability with rubber compositions, their strength, and other properties. These tests were then compared with the properties of the ceramic balloons described in the technical literature cited above, revealing that fly ash balloons were preferable. Therefore, various tests were conducted using fly ash (fly ash balloons) as the standard for ceramic balloons. Figure 3 shows the properties of fly ash. Its main components are silica (SiO2) and alumina (Al2O3), and its compressive strength is 70 MPa. A magnified photograph of the fly ash reveals that the particle shape is spherical and the particle wall thickness is uniform. Air bubbles are also observed within the particle walls. [Example]

[0022] Wet friction tests were conducted to confirm the characteristics of rubber compositions containing ceramic balloons. The rubber compositions used were hydrogenated nitrile rubber (HNBR) and chlorosulfonated polyethylene rubber (CSM). Fly ash with a particle size of 100 μm was used as the ceramic balloons, and 5% by mass of the rubber composition was added. The friction test was conducted using the friction tester shown in Figure 4. This friction tester involves placing a stainless steel strip (0.6 mm thick, 14 mm wide) on a rotating roller whose surface is made of rubber composition, and pouring water from above at a flow rate of 500 ml / min. The winding angle θ of the stainless steel strip around the rotating roller is 90°, and the pressing force applied to the surface of the rotating roller is varied by varying the load W between 10 and 40 kg, as shown in Figure 4. The test force detected by the load cell at this time is T. The rotation speed of the rotating roller can be varied between 5 and 40 rpm. The friction coefficient (wet friction coefficient) μ was calculated using μ = 1 / (θ log E(T / W)).

[0023] The results of the friction tests are shown in Figures 5 and 6, and in Tables 1 and 2. HNBR+CB and CSM+CB shown in the figures indicate rubber compositions containing 5% by mass of fly ash with an average particle size of 100 µm. In the graph shown in Figure 5, the horizontal axis represents the load W, and the vertical axis represents the static friction coefficient µ. In the graph shown in Figure 6, the horizontal axis represents the rotation speed N, and the vertical axis represents the dynamic friction coefficient µ. Table 1 shows the average values ​​of the measured friction coefficients. Table 2 shows the ratio of each friction coefficient to the average value.

[0024] [Table 1]

[0025] [Table 2]

[0026] As shown in Figures 5 and 6 and Tables 1 and 2, by incorporating ceramic balloons into a rubber composition, the coefficient of friction increases by more than two times, and the dynamic coefficient of friction in particular. Furthermore, the effect of increasing the coefficient of friction differs depending on the rubber composition, and CSM is more preferable than HNBR as a rubber composition (rubber composition itself without ceramic balloons). Furthermore, Figures 5 and 6 show that there is little difference in the static or dynamic coefficient of friction between CSM and HNBR as rubber compositions. By incorporating ceramic balloons into a rubber composition, the static coefficient of friction can be increased by 1.2 to 2.4 times, and the dynamic coefficient of friction can be increased by 1.5 to 3 times. [Example]

[0027] As a rubber composition, CSM is preferred as shown in Example 1, but chloroprene rubber (CR) is also preferred, and CSM and CR are attracting attention as ceramic-containing rubber compositions. In addition, in light of the fact that carbon black and silica are generally used as additives in rubber compositions, the following tests were conducted using rubber containing at least one of chlorosulfonated polyethylene rubber (CSM) and chloroprene rubber (CR), or rubber containing carbon black or silica in these rubbers (hereinafter referred to as rubber mixed composition) as the standard rubber composition.

[0028] A test was conducted to examine the effect of ceramic balloon content using a rubber mixed composition containing fly ash with an average particle size of 100 μm. The test results are shown in Table 3. In Table 3, "normal" refers to a rubber mixed composition that does not contain ceramic balloons. Grip properties were measured using the friction tester shown in Figure 4. Abrasion resistance was measured using an abrasion tester conforming to JIS K7204. Table 1 shows that the ceramic balloon content is preferably 1 to 15%.

[0029] [Table 3]

[0030] Table 4 shows the results of investigating the effect of the average particle size of the ceramic balloons. Fary ash was used as the ceramic balloons. 5% by mass of Fary ash was included in the above rubber composition. Table 4 shows that ceramic balloons with a particle size distribution of 20 to 300 μm are preferred.

[0031] [Table 4] [Example]

[0032] Surface roughness measurements were conducted on an example of the invention, in which the rubber composition contained ceramic balloons (fly ash, average particle size 100 μm, content 5% by mass), and a comparative example, in which the rubber composition was nitrile rubber (containing no ceramic balloons). Surface roughness was measured as the arithmetic mean roughness Ra and the maximum cross-sectional height Rt (JIS B0601). The test results are shown in Figure 7. Comparing the roughness curves of the example and comparative example, the comparative example exhibits a smooth overall roughness curve, whereas the example exhibits areas of increased roughness at relatively short intervals, even within a narrow range (1 to 8 mm), with some particularly high roughness areas. These characteristics are believed to be due to the state of the fracture surfaces of the ceramic balloons scattered on the surface of the rubber composition. Furthermore, the arithmetic mean roughness Ra of the example was 1.7 times that of the comparative example, and the maximum cross-sectional height Rt of the example was 1.9 times that of the comparative example, suggesting a significant effect due to the scattered fracture surfaces of the ceramic balloons. [Example]

[0033] A CTV equipped with a fender (example) with a rubber mixed composition (fly ash, average particle size 100 μm, content 5% by mass) on its surface layer was maneuvered in a wave-making tank to conduct a test to confirm the effectiveness of the fender. As a comparative example, a fender with a nitrile rubber (not containing ceramic balloons) on its surface layer was installed on the CTV and tested. The scale of the CTV was 1 / 12.8 of that of an actual crew transport ship. The test conditions were as follows: a bottom-mounted offshore wind turbine (OWT) was placed in the wave-making tank, and the bow of the CTV was pressed against the launch and landing area, and the up-and-down motion of the bow was measured in a significant wave height of 2.5 m. Figure 8 shows the test results. As shown in Figure 8, waves flow from the bow to the stern of the CTV, so when the water level rises from the bow of the CTV, it rides the inclination caused by the waves and recedes. For this reason, as shown in Figure 8, in both the invention example and the comparative example, the fender loses its gripping force, causing the bow to rise momentarily, followed by a sudden drop immediately afterwards. However, in the case of the invention example, once the bow of the CTV passes the wave peak and is pressed against the OWT again, the gripping force is instantly restored, and the CTV is maintained at the specified height. On the other hand, in the comparative example, the bow of the CTV sinks deep and descends to a certain extent, and then the CTV finally gains buoyancy and rises, but with large up and down movements.

[0034] Based on the above test results, it is estimated that a CTV equipped with the inventive fender can be used on an actual ship at sea with a significant wave height of 2.5m, and is fully usable at a significant wave height of 1.5m. Note that significant wave height refers to the average wave height of the first one-third of the waves observed at a certain location over a certain period of time (for example, 20 minutes). This is said to be close to the wave height observed by human observation, and wave height forecasts are based on the "significant wave height." (https: / / www.jma.go.jp / jma / kishou / know / yougo_hp / nami.html)

[0035] Table 5 is a table that calculates the degree of availability that can be achieved for significant wave heights using oceanographic data for the northern sea area of ​​the Sea of ​​Japan. In the examples of the invention, the surface layer of the fender contains ceramic balloons (fly ash, average particle size 100 μm, content 5% by mass) in a rubber mixed composition. In the comparative examples, the surface layer of the fender is made of a styrene-butadiene rubber composition, with Comparative Example 1 having wave-shaped grooves on the surface and Comparative Example 2 having the raw material surface without grooves. In the examples of the invention, the significant wave height is 2.5 m. The significant wave heights of the comparative examples were 1.5 m for Comparative Example 1 and 1.0 m for Comparative Example 2. It can be seen that a CTV equipped with the fenders of the examples of the invention has an availability of 90%, meaning that it can be operated almost throughout the year.

[0036] [Table 5] [Explanation of symbols]

[0037] 10 Fender 11 Rubber composition 15 Ceramic Balloons 151 Broken ceramic balloon 17 Additives

Claims

1. A fender for a worker transport ship that is operated alongside a facility installed in a water area, wherein the rubber composition that forms the surface layer of the fender contains hollow ceramic balloons, and the surface of the rubber composition is polished so that broken pieces of the ceramic balloons are scattered throughout.

2. 2. The fender according to claim 1, wherein the polished surface of the rubber composition has an Ra of 2 to 7 μm and an Rt of 20 to 100 μm.

3. 3. The fender according to claim 1, wherein the rubber composition contains 1 to 15 mass % of ceramic balloons.

4. 3. The fender according to claim 1, wherein the ceramic balloons have a particle size distribution of 20 to 300 μm.

5. 3. The fender according to claim 1, wherein the ceramic balloon has a breaking stress of 100 to 300 MPa.

6. 3. The fender according to 1 or 2, characterized in that the rubber composition is a rubber containing at least one of chlorosulfonated polyethylene rubber (CSM) and chloroprene rubber (CR), or a rubber obtained by adding carbon black or silica to any of the above rubbers.

7. A fender for a worker transport ship that is operated alongside a facility installed in a water area, The rubber composition forming the surface layer of the fender contains hollow ceramic balloons, and the fender has a static friction coefficient of 0.4 to 1.2 and a dynamic friction coefficient of 0.3 to 0.7 in a wet state. The friction coefficient was determined using a wet friction tester manufactured in-house.

8. A fender to be installed on a worker transport ship that is operated alongside a facility installed in a water area, the fender having a surface layer comprising the following ceramic balloon-containing rubber composition. The coefficient of friction of the rubber composition containing ceramic balloons in a wet state is 1.2 to 2.4 times higher for static friction and 1.5 to 3 times higher for dynamic friction than the coefficient of friction of the rubber composition itself that does not contain ceramic balloons. The coefficient of friction was determined using a wet friction tester manufactured in-house.

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